1. Field of the Invention
This invention generally relates to an apparatus for protecting an occupant in a vehicle such as an automotive vehicle. This invention particularly relates to a vehicular occupant protecting apparatus including image taking devices such as cameras or area image sensors.
2. Description of the Related Art
A known apparatus for protecting an occupant in a vehicle includes a pair of area image sensors located near a vehicle windshield and facing an area on a vehicle seat. The area image sensors are spaced at a prescribed interval along the widthwise direction (the transverse direction) of the vehicle. The area image sensors take images of the area on the vehicle seat, and output signals representing the taken images. In the known apparatus, the image-representing signals are processed to detect the positions of portions of an occupant on the seat. The detected positions are defined along the lengthwise direction (the longitudinal direction) of the vehicle. The mode of the control of deployment of an air bag is changed in response to the detected positions of the portions of the occupant.
In the known apparatus, shifts between corresponding portions of the images taken by the area image sensors are detected, and the positions of portions of an occupant are measured from the detected shifts on a triangulation basis. In the known apparatus, the triangulation-based detection of the positions of portions of an occupant includes complicated image-signal processing which causes a longer signal processing time. The longer signal processing time is a factor obstructive to the quick control of deployment of the air bag.
European patent application publication number EP 0885782 A1 which corresponds to Japanese patent application publication number 11-15980 discloses an apparatus for detecting the presence of an occupant in a motor vehicle. The apparatus in European application EP 0885782 A1 includes a pair of cameras for producing first and second images of a passenger area. A distance processor determines distances that a plurality of features in the first and second images are from the cameras based on the amount that each feature is shifted between the first and second images. An analyzer processes the distances and determines a size of an object on the seat. Additional analysis of the distances also may determine movement of the object and the rate of that movement. The distance information also can be used to recognize predefined patterns in the images and thus identify the object. A mechanism utilizes the determined object characteristics in controlling deployment of an air bag.
U.S. Pat. No. 4,625,329 which corresponds to Japanese patent application publication number 60-152904 discloses an image analyzer for analyzing the position of a vehicle driver in a three-dimensional coordinate system. The analyzer comprises a light emitting element for emitting an infrared light beam to the driver's face portion, and an image detector arranged to receive reflected infrared light and generate an optical image of the driver's face portion. A microcomputer includes a memory for storing an electronic image corresponding to the optical image.
The microcomputer processes the stored image to determine the position of a facial feature, such as an eye, in a three-dimensional coordinate system. The position indicating data are utilized in a driver assistance system.
Japanese patent application publication number 11-43009 discloses that an ultrasonic-wave transmitter/receiver measures the distance to an occupant in a vehicle, and the measured distance is utilized in determining the position of the occupant relative to an air bag. Deployment of the air bag is controlled in response to the determined relative position of the occupant. Japanese application 11-43009 also discloses that the position of an occupant in a vehicle can be detected by using two CCD arrays spaced from each other. Japanese application 11-43009 further discloses that a combination of a CCD array and a pattern recognition software takes an image of the head of an occupant in a vehicle and accurately detects the position of the head.
Japanese patent application publication number 10-315906 discloses an air-bag control system including an infrared sensor of a matrix type. The infrared sensor outputs data representing a thermo-based image. The image data are processed in response to a signal representative of a first threshold value to extract a portion of the image which corresponds to the body of an occupant in a vehicle. The image data are further processed in response to a signal representative of a second threshold value to extract a portion of the body image which corresponds to a face of the occupant. The position of the occupant's face is calculated from the positions of ones among the elements of the matrix of the infrared sensor which correspond to the occupant's face. An offset of the calculated position of the occupant's face from a reference position is computed. The offset is utilized in controlling the amount of air introduced into an air bag and also the direction of the gas introduction.
Japanese patent application publication number P2001-116841A discloses that an automotive vehicle is provided with a plurality of sensors for measuring the distances to a head of vehicle's occupant. The position of the head of the vehicle's occupant is determined in response to the measured distances.